The present invention relates to a monitored, controlled door installation, such as the type employed in penal institutions or the like and more specifically, to an improved door position monitoring arrangement including novel structure for automatically adjusting or aligning the monitoring arrangement for operation with a given degree of door movement from the secured or closed position.
Penal institutions or the like often employ monitoring and control apparatus for cell doors or the like. Accordingly, when it is desired to control access to a number of doors at any one time, it is desirable that a display panel or the like provide a correct indication as to the open or closed condition of each of the doors to be controlled. To attain the desired monitoring of the status of each door, various types of apparatus are used, which are responsive to door position and capable of providing a control signal in relation thereto.
In this regard, the prior art has provided a door lock mechanism which generally includes a monitoring switch which is operated from a first or "door-open" position to a second or "door-closed" position when the door is fully closed. When the door is open or ajar slightly, however, these switches and the lock mechanism are often accessible and hence can be operated manually to give a false signal that the door is closed and locked, when in fact it is not.
To augment this type of lock monitoring arrangement, it is a relatively common practice to employ a second door position monitor that cannot be easily circumvented. The respective door position monitors are then connected essentially in series circuit with a display panel so that a "door secure" signal is provided only when both monitors detect the closed position of the door. As such, ideally the second monitoring arrangement should be of a type that will give the "door secure" signal only when the door is substantially at the fully, and completely closed position. In this condition, the engagement of the door with the door stop and its alignment with the door jamb preclude manual overriding of the lock apparatus and the monitoring switch associated therewith.
One type of known secondary or supplemental monitoring arrangement employed in the art provides a switch which is associated with a hinge-type actuator, and is operated as a result of the pivotal movement of the door about the axis provided by the door hinges. The problem with this arrangement, however, is that the sensitivity of available switch designs is such that a certain minimum amount of movement of the operating arm for the switch is required before the switch is operated from one condition to another.
Since the operational movement for the switch is produced as a result of the pivotal movement of the door at the hinge, there exists with these prior art arrangements, a considerable play or range of arcuate movement of the door at the outer edge thereof that can take place when the door is moved before the switch is actuated. It will be appreciated in this regard that but a few degrees of movement of the door at the hinge will often result as much as one or two inches of movement of the free edge of the door at the door jamb proximate the lock. Openings of this size can be sufficient to enable manual overriding of the lock and the monitoring switch associated therewith so that the display panel may register a "door secure" condition when in fact a door is ajar and not secured.
One particularly advantageous system for overcoming the foregoing problem is shown in my prior U.S. Pat. No. 4,334,388. This arrangement attains sensitivity of operation through the arrangement and construction of the various elements of the overall assembly, while using conventional switch components. More specifically, with the prior art type of monitoring arrangements as discussed above, the ratio of door movement to movement available for operation of the monitoring switch was 1:1; that is, one degree (1.degree.) of door movement produced but one degree (1.degree.) of rotational movement about the hinge axis for transmittal to the switch actuating mechanism. In contrast, the arrangement provided in my aforesaid patent increases this ratio by moving the operational pivot for the switch actuating mechanism away from the pivotal axis of the door as defined by the hinges, and by connecting the pivotally mounted door to said actuating mechanism by a control arm which is slidably connected to the door, yet will pivot relative to the switch actuating mechanism. As is detailed more fully in the aforesaid patent, a ratio of actuator movement to door movement of 1.55:1 is easily attained. Thus, by way of example, with the prior art two degrees (2.degree.) of door travel will result in only two degrees (2.degree.) of rotational movement at the hinge axis, approximately three degrees--five minutes (3.degree. --5') of actuator movement is obtained.
While the foregoing patented system has proved successful there is room for yet further improvement. For example, the patented system requires some final adjustment during installation to "fine tune" the monitoring assembly for operation with a particular door and door frame.
The present invention advantageously eliminates the need for any particular skill or experience on the part of the installer, by greatly simplifying the installation procedure in this regard. That is, the present invention presents an automatically adjustable or self-aligning feature which eliminates the need for such "fine tuning" or fine adjustments upon installation.